When an engine is not operated for a period of time, the engine oil drains down into the reservoir, leaving the engine components less than optimally lubricated. During engine start-up, unlubricated surfaces contact causing frictional wear before the engine oil pump can circulate an adequate oil supply. One approach to alleviate this concern is to provide a prelubrication system. This system may require a separate supply conduit and a separate external motor driven pump to lubricate the engine and turbocharger before engine start-up.
During hot shut-down of an engine with a turbocharger, the turbocharger will continue to spin for a period after the engine oil pump has shut off. Heat may build up as the bearings are not lubricated during this time. It is desirable to maintain lubrication flow to reduce soakback heat and frictional wear to extend bearing life. One solution is to provide a postlubrication system. Such a system may require an external motor driven pump and a designated conduit system.
Many engine applications use two separate systems described above to accomplish pre and postlubrication. Dual systems require separate controls, conduit system, motors and pumps, which increase cost, weight, and packaging requirements.